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摘要 : 剪接(非编码RNA从pre-mRNA转录体的切除)中所涉及的中心复合物是tri-snRNP。这一复合物含有三个 “小核RNA” (snRNAs)和超过30个蛋白。

 剪接(非编码RNA从pre-mRNA转录体的切除)中所涉及的中心复合物是tri-snRNP。这一复合物含有三个 “小核RNA” (snRNAs)和超过30个蛋白。Kiyoshi Nagai及同事现在通过 “单粒子低温电子显微镜”确定了这一复合物的结构。其分辨率足以以前所未有的详细程度显示在解旋、外显子排列和催化中所涉及的区域。


The architecture of the spliceosomal U4/U6.U5 tri-snRNP


U4/U6.U5 tri-snRNP is a 1.5-megadalton pre-assembled spliceosomal complex comprising U5 small nuclear RNA (snRNA), extensively base-paired U4/U6 snRNAs and more than 30 proteins, including the key components Prp8, Brr2 and Snu114. The tri-snRNP combines with a precursor messenger RNA substrate bound to U1 and U2 small nuclear ribonucleoprotein particles (snRNPs), and transforms into a catalytically active spliceosome after extensive compositional and conformational changes triggered by unwinding of the U4 and U6 (U4/U6) snRNAs. Here we use cryo-electron microscopy single-particle reconstruction of Saccharomyces cerevisiae tri-snRNP at 5.9 Å resolution to reveal the essentially complete organization of its RNA and protein components. The single-stranded region of U4 snRNA between its 3′ stem–loop and the U4/U6 snRNA stem I is loaded into the Brr2 helicase active site ready for unwinding. Snu114 and the amino-terminal domain of Prp8 position U5 snRNA to insert its loop I, which aligns the exons for splicing, into the Prp8 active site cavity. The structure provides crucial insights into the activation process and the active site of the spliceosome.

来源: Nature 浏览次数:0


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